[time-nuts] Fundamental limits on performance

Mark Spencer mspencer12345 at yahoo.ca
Thu Sep 17 16:09:41 UTC 2009

Apparently there are also concerns that the ability to produce crystals in glass enclousres going forwards may be in doubt as the required industrial base continues to shrink.  

----- Original Message ----
From: Chris Caudle <chris at chriscaudle.org>
To: time-nuts at febo.com
Sent: Wednesday, September 16, 2009 8:15:14 PM
Subject: Re: [time-nuts] Fundamental limits on performance

> From: Mark Spencer <mspencer12345 at yahoo.ca>
> For anyone who is interested here is a bit more info about the USO's used
> in deep space applications and some comments abou the crystal based USO's

I found it interesting that one of the limits of stability seems to be the
ability to process the crystals at high temperatures to drive off
impurities.  The JHU crystals are apparently in some type of glass
enclosure which can take the high temperatures, and the paper seemed to
indicate that the standard metal capped packages can't take the higher

I had forgotten until I read that paper that Fox has crystals which are
packaged in quartz packages.  I couldn't find any information on how the
packages are assembled, so I don't know if the assembly process could
handle the higher temperatures, but obviously if the package really is
pure quartz, it should be able to handle temperatures as high as the
quartz resonator.  I would assume that the package is in two parts, and
has contacts that penetrate the lower part of the package to connect the
resonator to the surface mount pads on the bottom surface of the package,
so it might depend on how the penetration is sealed, and how the top and
bottom parts of the package are attached together.

Just seemed interesting, I would assume that the JHU guys know about those
types of advances in packaging, but the paper didn't mention it.

Chris Caudle

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